Temperature compensated bubble for panoramic sextants



y March 16,1943.

.J.- :RANE Erm. 2,313,734

TEMPERATURE COMPENSATED BUBBLE `FOR PANORAMIC SEXTANT Ovriginal FiledMarch 14, 1940 Patented Mar. 16, 1943 UNITED STATES PATENT OFFICETERIPERATURE COMPENSA'IED` BUBBLE FOR PANORAMIC1 SEXTANTS Carl J. Crane,Shreveport, La., and Samuel M. Burka, Dayton, Ohio 1941, Serial N0.398,844

2 Claims.

The invention described herein may be manufactured and used by or forthe Goverment for governmental purposes, without the payment to us ofany royalty thereon.

This application is a division of application Serial No. 323,964, ledMarch 14, 1940 now Patent No. 2,280,798 granted April 28, 1942.

This invention relates to uid levels and particularly to bubble levelsused in connection with instruments such as sextants and the like.

It is an object of this invention to provide means for controlling thesize of the bubble in a iluid level.

It is another object of this invention to provide means for varying thesize of a fluid level bubble at will.

It is a further object of this invention to provide temperature controlmeans for controlling the size of the bubble and for varying its size atwill.

Other objects and advantages of the invention will become apparent fromthe following detailed descriptions of the invention, reference beinghad to the accompanying drawing wherein:

Fig. 1 is a cross sectional view of the lower portion of a sextantincorporating the present invention;

Fig. 2 is a cross sectional View taken along the lines 2-2 of Fig. 1;and

Fig. 3 is a diagrammatic view of the bubblecell heating circuit.

Referring to the drawing, the bubble-cell 23 received in chamber I8 isoperatively positioned in the lower end of the sextant housing 2 in sucha manner as to receive image-carrying light rays reflected by mirrors 2|and 22 in reilector chamber I'I. These rays pass through orice I9 andbubble 23 and are reflected by the inclined reflector 34 through lenses39 so as to be observable in eye piece 31. The eye lens unites in thedrum I 6 incorporating the low power lens 39 and the high power lens 4|for observing the images of the observed objects and the bubblecell isas described in the aforementioned application of which this is adivision.

(Granted under the act of March 3, 1883, las amended April 30, 1928; 3700. G. 757) Coming now to the subject matter of the instant invention,bubble-cell 23 is of a conventional and well known construction in whichthe bubble moves on the under side of the spherical surface of the topcover glass. The uid in the level is of any suitable substance. In viewoi the fact that substances suitable for bubble levels are lsulzijectedto expansion and contraction under varying temperature conditions, thebubble level is provided with a heating element 30, the temperature ofwhich is controllable by a rheostat 3| adjustable by means of knob 32.Electrical energy for heating purposes may be supplied by a suitablesource 33.

As described in the aforementioned application, the bubble-cell isprovided with a cross mark 28 to be used for taking bearings; a light 29for illumination of the bubble; a door 24 for the opening I8; a nut 25for holding the door closed; a spring 26 carried by the door and adaptedto engage a, projection |`I in the bubblecell 23 for positioning thesame in the chamber I 8.

It is obvious that various modications can be made without departingfrom the spirit and scope of the present invention as pointed out in theappended claims.

We claim:

1. A bubble-cell having means by which the size of the bubble may bechanged at will, said means comprising an electrical heating circuitincluding a heating element within the cell and a rheostat forcontrolling the temperature of the heating element.

2. A bubble-cell having in combination, top and bottom plates of glassbetween which the bubble is conned, a source of potential, a heatingelement between the said plates of glass and a rheostat for controllingthe temperature of the heating element, said heating element andrheostat being connected in electrical circuit with said source ofpotential.

CARL J. CRANE. SAMUEL M. BURKA.

